Within a mobile telecommunications system plural mobile User Equipment, UE, is active. Among which Mobile Telephones, Personal Digital Assistants, Mobile Personal Computers and many other communication devices. Each mobile UE comprises a Subscriber Identity Module, SIM, card comprising the Mobile Subscriber Integrated Service Digital Network, MSISDN, number. In the following called the mobile subscriber number. A mobile UE of a user can not operate without a physically attached SIM card. Without the SIM card in place there is no identification of the mobile subscriber number and neither is pre-paid or post-paid charging possible.
The physical presence of a SIM card with a mobile UE causes restrictions of the freedom of use of a mobile subscriber number of a user.
In a situation where two or more users want to share a same mobile UE, they can only do so by physically replacing the SIM card. Another situation wherein a single user owns two or even more mobile subscriber numbers and the user wants to use both mobile subscriber numbers on the same or on different devices, he or she has to swap SIM cards.
A possible solution to the problem of swapping SIM cards is to use a mobile UE which is capable of physically attaching two SIM cards, a so called dual SIM compatible mobile UE. Although this provides a solution to a single user owning a mobile UE and two SIM cards, there are serious restrictions. Only a few mobile UE available nowadays are compatible for using two SIM cards, therefore limiting the choice of using a particular mobile UE. Besides that dual SIM mobile UE are more expensive then single SIM mobile UE. This solution does also not apply for users who want to use more than two SIM cards.